Updated September 2026: Google Ads still provides two ad-rotation settings for eligible Search, Shopping and Display campaigns: Optimize and Do not optimize. The setting controls how multiple ads in an ad group are served relative to one another; it is not the same thing as running a statistically clean experiment.
What ad rotation does
If an ad group contains multiple eligible ads, Google decides which one enters each auction. Ad rotation influences that serving behavior. Only one ad from your account can show in a given auction.
Option 1: Optimize
Optimize is the default choice for most performance campaigns. Google uses auction-time signals such as query, keyword, device and location to favor the ad expected to perform better. With Smart Bidding, conversion likelihood can also influence delivery.
When I use Optimize
- Always-on performance campaigns.
- Ad groups using responsive search ads and Smart Bidding.
- Accounts where the goal is conversions rather than equal impression distribution.
Option 2: Do not optimize
This setting rotates ads more evenly rather than deliberately favoring the predicted winner. It can be useful in limited testing situations, but equal-ish serving does not automatically make the test statistically valid because auctions, eligibility and other conditions still vary.
Do not confuse ad rotation with Experiments
If you need a controlled test of bidding, landing pages, campaign settings or materially different strategies, Google Ads Experiments is usually a better methodology than relying only on ad rotation.
How responsive search ads changed ad testing
Modern Search campaigns normally use responsive search ads, where Google combines headlines and descriptions dynamically. That means the more useful question is often not “which complete ad won?” but “which message themes, assets and landing-page combinations produce qualified conversions?”
What to measure
- Qualified conversion rate.
- Cost per qualified lead or acquisition.
- Conversion value / ROAS where relevant.
- Search-term quality.
- Asset performance and ad strength as diagnostics, not final business KPIs.
My 2026 recommendation
Use Optimize for most mature performance campaigns. Use Do not optimize only when you have a specific testing reason and enough volume. For strategic tests, use campaign experiments and judge the result by business outcomes rather than CTR alone.
For a broader account review, see my Google Ads Audit Checklist 2026.